Pyrrolizidine alkaloid clivorine induces apoptosis in human normal liver L-02 cells and reduces the expression of p53 protein.

Clivorine, a pyrrolizidine alkaloid, is a potent toxic compound extracted from a Chinese medicinal plant Ligularia hodgsonii Hook. We have previously shown that clivorine inhibited human normal liver L-02 cells proliferation and induced p38 mitogen-activated protein kinase phosphorylation. The aim of this study is to further observe the mechanism of clivorine-inhibited L-02 cells growth. In this paper we show here that clivorine can induce apoptosis in L-02 cells, reduce the expression of p53 protein but has no effect on the expression of Bcl-2 protein, and clivorine also induces the cleavage of the poly(ADP-ribose) polymerase in L-02 cells. Our results suggest that the anti-proliferative function of clivorine in L-02 cells may be due to its inducing cell apoptosis, and clivorine-induced cell apoptosis is independent of p53 protein.